The Effects Of Magnetic Properties And Thermal Expansion Behaviors Of Rare-Earth Compounds From Cr And Si Substitute

By means of X-Ray diffraction and magnetization measurements, this paper studies the crystal structure, magnetic properties and thermal expansion behaviors of R2Fe17(R=Tm, Gd) compounds. The effect of substitution of Cr and Si on the crystal structure, Curie temperature and spontaneous magnetization of R2Fe17(R=Tm, Gd) compounds are analyzed and discussed in detail.The research results of Tn12CrFe16-xSix(x=0,0.5,1.0,1.5,2.0,2.5,3.0) compounds prepared by the electric arc furnace indicate that Tm2CrFe16-xSir(x=0,0.5,1.0,1.5,2.0,2.5,3.0) compounds has Th2Zn17-type structure at room temperature (-300K) With the increase of substituting amounts of Si, the unit-cell parameters of compounds decrease monotonously and nonlinearly, which is related to atomic volume and magnetic interaction. The investigations of magnetic indicate that the Curie temperature of Tm2CrFe16-xrSix compounds is raised by the substitution of Si, and the maximum is450K when x=1.5. Besides with the increase of substituting amounts of Si the spin reorientation temperature also rises monotonously to maximum value:220K (x=3.0). This shows that the uniaxial magnetocrysalline anisotropy increases with increasing substituting amounts of Si. Compared with research results of substitution of Si or Cr alone, it is deduced that the effect on the Curie temperature and magnetocrysalline anisotropy of their respective substitution for different crystall sites can be superimposed in some degree. Research results of spontaneous magnetization of compound at room temperature indicate that it decreases monotonously with the increase of substituting amounts of Si, which results from the substitution of Non-Magnetic Atom Si for Magnetic Atom Fe.The research results of Gd2Fe17-xCrx (x=0,0.5,1.0,3.0) compounds prepared by the electric arc furnace indicate that Gd2Fe17-xCrx (x=0,0.5,1.0,3.0) compounds has Th2Zn17-type structure. With the increase of substituting amounts of Cr the volume of unit-cell decreases monotonously. The investigations of magnetic indicate that the Curie temperature of Gd2Fe17-xCrx compounds is raised by the substitution of Cr, and the max is about575K when x=1.0It is found that strong spontaneous magnetostriction phenomenon exists in Gd2Fe17-xCrx compounds, with which thermal expansion combined results in anomalous thermal expansion of Gd2Fe17-xCrx compounds in a certain temperature range. Through variable temperature X-ray diffraction temperature dependence of the unit-cell parameters of compounds is obtained. And through further study based on the Debye theory and the Gruneisen relation, rules of change with the temperature of body magnetostrictive coefficient ωs, line magnetostrictive coefficient λc and line magnetostrictive coefficient λα of Gd2Fe17-xCrx compounds are figured out. Results indicate that at the same lower temperature λc is much larger than λα.